Protecting the Liberty Bell

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On July 4th, many Americans will travel hundreds of miles to visit the Liberty Bell in Philadelphia. But at this time in 2003, the bell was getting ready for its own trip--roughly 200 yards from its existing location into a new museum. Moving the 250-year-old bell over even that short a distance, however, might have caused a catastrophic break. NSF-supported engineers proved critical to keeping the icon safe.

A long, hairline fracture extends from the Liberty Bell's famous crack, and the National Park Service was worried that the fracture could split open during the stresses of the move. But they wouldn't know unless they could find a way to measure accurately extremely tiny movements in the metal as the 2,000-pound bell was raised. Engineer Steve Arms and his colleagues from MicroStrain, Inc. in Williston, Vt., had developed tiny, wireless motion sensors with the help of NSF funding, and the bell's handlers realized that the devices would be perfect for warning of dangerous motion along the crack on moving day.

During a test lift, as the famous bell was gingerly lifted a few inches off its mount, the engineers used customized versions of their sensors to carefully measure strain on the metal, information that the team then used to monitor the bell closely as it eventually, and safely, made its journey on Oct. 8 to its present home at the new Liberty Bell Center.

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2017, its budget is $7.5 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 48,000 competitive proposals for funding and makes about 12,000 new funding awards.